Is Your B12 Deficiency Causing That Tingling in Your Feet?

If you've noticed tingling, numbness, or a pins-and-needles sensation in your feet — particularly at night — you're experiencing what medicine calls peripheral neuropathy. It's one of the most common neurological complaints in adults over 45, affecting an estimated one in five people over 60. And while it has many causes, one of the most frequently overlooked and most reversible is vitamin B12 deficiency.

The critical word in that sentence is reversible. Catch a B12-driven neuropathy early enough, and the nerve damage can be halted and often partially reversed. Leave it too long, and the damage becomes permanent. This is why understanding the mechanism — and getting tested — matters.

What B12 Does for Your Nervous System

Vitamin B12 (cobalamin) is essential for the synthesis and maintenance of myelin — the protective sheath that surrounds nerve fibres. Think of myelin as the insulation around an electrical cable. When it degrades, signals travelling along the nerve become distorted, slowed, or lost entirely.

B12 deficiency causes a specific pattern of myelin breakdown called subacute combined degeneration. In the peripheral nervous system — the network of nerves running from your spine to your hands and feet — this manifests initially as tingling and numbness in the extremities, typically starting in the feet and working upward. In later stages it affects balance, coordination, and cognitive function.

"B12 deficiency is a slow-moving crisis. Symptoms can develop over months or years before reaching a threshold where the person seeks medical attention — by which point significant nerve damage may already have occurred."

Why B12 Deficiency Is More Common After 45

Dietary B12 from food (meat, fish, eggs, dairy) must be separated from its food-bound protein in the stomach using hydrochloric acid, then bound to a carrier protein called intrinsic factor before it can be absorbed in the small intestine. After 45, two things reliably go wrong with this process:

• Gastric acid production declines with age — a condition called atrophic gastritis affects up to 30% of adults over 50. Less acid means less efficient release of B12 from food, even if dietary intake is adequate.
• Common medications interfere with absorption. Proton pump inhibitors (PPIs) — widely prescribed for acid reflux — suppress gastric acid and measurably reduce B12 absorption with long-term use. Metformin, used for type 2 diabetes, depletes B12 through a separate mechanism affecting intrinsic factor. Both drugs are among the most commonly prescribed in the over-50 population.

This is why serum B12 can be low even in people with seemingly adequate dietary intake — the problem is absorption, not ingestion.

Recognising the Symptoms

B12 deficiency neuropathy typically presents as a symmetrical pattern of symptoms in both feet before affecting the hands. The progression, if left unaddressed, follows a recognisable sequence:

1. Tingling or pins-and-needles in the toes and soles of the feet
2. Numbness or reduced sensation in the feet and lower legs
3. Balance difficulties — often noticed when standing on uneven surfaces or in the dark
4. Weakness in the legs and, later, the hands
5. Cognitive changes, including memory difficulties and low mood

Many people attribute early neuropathy symptoms to "poor circulation" or simply ageing. This attribution delays investigation and treatment — which matters enormously, because the reversibility of B12 neuropathy is directly time-dependent.

Testing: What to Ask For

Standard serum B12 testing has a significant limitation: it measures total B12 in the blood, including inactive forms that cannot be used by cells. A serum B12 in the "normal" reference range does not rule out functional deficiency.

The more sensitive markers are:

• Methylmalonic acid (MMA): Elevated MMA is one of the earliest markers of functional B12 deficiency, rising before serum B12 falls below the normal range. This is the most reliable confirmatory test.
• Holotranscobalamin (Active B12): Measures only the biologically active fraction of B12. A low holotranscobalamin is a more sensitive indicator of early deficiency than serum B12 alone.
• Homocysteine: Elevated homocysteine suggests B12 (and/or folate) deficiency, though it is less specific.

If you are experiencing symptoms consistent with peripheral neuropathy and are over 45, request these tests — not just a standard B12 level — from your GP or primary care physician.

Treatment Options

If deficiency is confirmed, the treatment approach depends on the underlying cause:

• For absorption problems (atrophic gastritis, PPI use): Oral supplementation at high doses (1000mcg daily) bypasses the intrinsic factor pathway through passive diffusion — effective in most cases. Sublingual (under-tongue) formulations improve this further.
• For severe deficiency or pernicious anaemia: Intramuscular B12 injections bypass the digestive system entirely and produce faster repletion. Often used when neurological symptoms are significant.
• For metformin users: Oral or sublingual supplementation is effective, but close monitoring is recommended. Discuss with your prescriber.

Symptom improvement with treatment is gradual. Tingling and numbness typically improve within 3–6 months of consistent supplementation. Balance difficulties take longer. In cases where deficiency has been longstanding, some deficit may be permanent — which is why early identification matters so much.

The Practical Takeaway

If you are over 45 and experiencing tingling or numbness in your feet — even mildly — ask your doctor to investigate beyond a standard serum B12. Request MMA and holotranscobalamin. If you are on a PPI or metformin long-term, request baseline testing regardless of symptoms.

The window for meaningful reversal of B12 neuropathy is real, but it is not open indefinitely. The earlier you act, the more of that window remains available to you.